Boom for shovel excavators



'1,670,470 H. F MENCK BOOM FOR SHOVEI., EXCAVATORS Filed Dec..3l. 1924 2 Sheets-Sheet l May 22, 1928.

MayI 22, 1928.

H. F. MENCK Boom FOR sHoVEL EXCAVATORS Filed D90. A3]., 1924 2 Sheets-Sheet 2 Patented May 22 1928.A

uNirEiDl Is"ifi't'r'iais' PA'rsnr or Freie. y

:uns FRIEDRICH'MENCK, oF ALTONA, GERMANY; Assienon To 'riin Finn' or tinnen ,a Hammock GESELLSCHAFTMITPBESCHRNKTER HAFTUNG; or Ancona, een; y,

y MANY.

iiooiirronx siiovnn Excava'rons.

Application led December 31, 1924,' Serial No.` 7759,178, and n- Germany January 4; 1324.`

In the operation of shovel excavatorsit frequently occurs that the `shovel or bucket y untimely, that is to say before the excavae. tor has finished its rotative' or swinging movement, strikes the ground, thus subject ing thelparts and mechanisms of the :excav vators to1strains and shocks, which they cannot stand and which lead` towbreakages.

To meet this inconvenience by increasing the Strength of the parts, is not sufficient ,since` the increased weight inherent therewithfwill also increase the inertia of the swinging parts. f

The object of the `present invention istoovercomethesediiculties by a novel construction.`

This task is solved bymou'nting the boom rotatably onvthebaseuplate'y which is carriedoscillatorily about` a horizontal line by a rotative part `of theexcavator in such inanner that it is adapted tol rotate about its longitudinal axis.

pulled back in this position after oscillating `to one side or the other..

y rection of the arrows in Fi s.1 a'ndzQ; v

Figs. 4 and 5 are views similartoFig. 3, showing` the parts when the boomV has rotated on its longitudinal axis.

The boom a is mounted rotatively by a pivot pin I) on the base plate c and is provided witli lateral feet d resting on the base plate which itself is connected rotatably about a horizontal axis by end studs e tothe upper truck A of the excavator. Bearing plates cl may be attached to the base plate c for allowing the feet d to bear against. When the bucket or shovel is operated to execute a new cut into the ground to be excavated and strikes against a hard hindrance the i ossibility is given that the rotative part of t e` excavator continues its rotative movement for a certain angle on account of the rotatability of the boom a about its longitudinal axis, that is to say about the pivot pin Z2. There is no difficulty in arranging theparts in such manner that the angle about which the rotatable parts of the ex- By the aid of:.a`doublev acting spring ory by two springs ithebooin is; yieldingly held in its central position, ori

cavator can rotate-When continuing-the said 55 rotation .may become so large that the rota#k tive parts of theexcavator in reaching such angle, completely lose their impetus by the action of the usual rotation brake (not shown) lpresent in all shovel excavators@ The result of this is, that all injurious overstrainings or stresses are relieved froin't-he shovelbeain, the derrickand the rotary upper-part of the excavator. A sudden deadening `ofthe inertia of rotary parts is thus 65 not necessary,- but retarding pressures are kept within such limits` that they can be overcome by the usual-rotation brake.y

Ify desiredthe. booni a may be connectedl with retraction springs, which pull the boom 70 backinto its central position. In the con struction shown a helical spring g is are rangedfwithin a casing f, one end'ofthe i spring pressing against an end Wall L of the` `casing and the other end auainst a dis'kiz', Tt`

ing connected with: the base plate c by a link; o and4 a-piiraiid slot connection asshown.4 `The end wallk it` oppositethe-` endlwall zfhas an arnilc in line with the tension rod c. Pivotally connected with this 85 arm lc is thearinm of the bell crank lever m', n4, the arm nf of which being also connected 'witht-hebase plate czbya linko". Theparts-o, n', m and j are similar tothey parts .0, man ands-jonfthe other side. The'fgn spring or springs g niust be so powerful, that they can overcome the friction of the boom feet d on the base plate c or bearing plates d respectively. They increase the effeet of the rotation brake by the fact that 4the 95 spring which is compressed by the rotation of the booin about the pivot pin exerts aV moment of retardation on the rotary parts of the upper truck of the excavator in the saine direction as the rotation brake. spring and the rotation brake must be so diinensioned that the total eect of both parts is not too great. The use of one or two springs has the advantage that they hold the boom, even when excavating, in its 105 central` position. It may happen that the lateral forces, which arise on the shovel While the excavator is digging, will increase e other arni n of which` leverbe U0 The' 10o to such an extent that the shovel gives way laterally, thereb turning or twisting the boom about its llongitudinal axis. To prevent this twisting of the boom becoming too extensive, it is advisable to limit such turning by stops p and p against which the links o, o contact,

It the boom, on rotation ol the excavator and the shovel, strikes the ground and rotates, for instance,to the position shown in Fig. 4 the pin j will have moved upwardly and the pin j downwardly. Consequently the bell-crank lever m, n has been given a clockwise rotation by the link `0, While the bell-crank lever m', n', even `when the lost` motion in the pin and slot connection has been overconie, cannot rotate owing to the arm m. striking against the stop p. It results that the distance between the ends of the arms m and m is increased and the spring g pressed together owing to the disk being pulled towards the end wall t of the casing The strain ol' the spring then tends to return the bell-crank lever m, n into its former position, by pulling the pin downwardly and rotating the boom backn'ardly.

When the boom is rotated into the position shown in Fig. 5 the bcll-crank lever m', /L' is rotated in a counter-clockwise direction owing to the pin j having moved upwardly, while the bellcrank lever m, It is prevented from rotating by abutting against the stop Here again the distance between the ends .if the arms m and m is increased, the arm m having pulled the arm le and with it the easing f to thus move the end wall 71, towards the disk z' and thus to again compress the spring g, which tends to turn the bell-crank lever m', n', and by means of the pin j', the boom, back into yits former position again.

The novel construction has not only advantages that are ecient when the shovel is starting to dig, but also such, which are effective while digging. As has been explained when excavating frequently lateral pressures arise on the shovel. 'When the pressure is slowly increasing the rotary part of the excavator has time to give Way by turning to one side. When however the pressure occurs suddenly the inertia of the rotating parts ol the `excavator is so great that they cannot follow quickly enough. Then the side pressure will exert a bending strain within the shovel beam and a rotary strain in the boom or derrick and such strains may lead to ruptures.

Arranging the boom to rotate about its longitudinal axis has moreover the advantage, that on side pressures arising suddenly overstrainings or stresses are avoided, because the rotary part ot' the excavator need not be made to rotate suddenly, but quite by degrees by the gradually increasing pressure ot' the compressed spring, which exerts the rotary moment on the rotary parts of the excavator.

I claim:

l. A boom Vfor shovel excavators, coinprising, a base plate journalled oscillatorily about a horizontal axis on a rotary part of the excavator, and a pivot mounting the boom on the base plate for rotation about the longitudinal axis of the boom, and means including a double acting spring and bellcrank levers cooperating therewith for bias ing the boom about its pivot to its central position on the base plate.

Q. A boom for shovel excavators, eomprising, a `base platejournalled oscillatorily about a borizontalaxis on a rotarf part of the excavator, and a pivot mounting the boom on the base plate for rotation about the longitudinal axis of the boom, and a double acting Spring arranged to bias the boom about its pivot to its central position on the base plate, bell crank levers connected at their central points to the foot of the boom, each bell crank lever having its two ends operatively connected respectively to the base plate and to one end of the double acting spring. l

HANS FRIEDRICH MENCK. 

